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Sorption thermal battery has revealed vast potential of heat utilization to address the issue of long-term energy storage. A hybrid compression-assisted sorption thermal battery is presented for solar energy utilization, which aims to solve the mismatch of heat storage and supply in cold region. Thermodynamic performance of the hybrid sorption thermal battery in cold region is analyzed by using MnCl2–SrCl2 and MnCl2–CaCl2 working pairs and then compared with that of basic sorption type with internal heat recovery. It is demonstrated that when ambient temperature in winter ranges from −30 °C to -5 °C, energy and exergy efficiencies of hybrid thermal battery using different working pairs increase from 0.74 to 0.865 and 0.25 to 0.43, respectively. Energy efficiency of hybrid thermal battery is almost twice higher than that of basic type with internal heat recovery. For different operating parameters, mass ratio and global conversion rate have a larger influence on thermal performance than isentropic efficiency of compressor. Although energy storage density per salt of basic sorption thermal battery is a bit higher than that of hybrid type, the density per reactor of hybrid compression-assisted thermal battery could be improved by 50%, which indicates a good system compactness in real application.

Closed-loop geothermal energy recovery technology has advantages of being independent of reservoir fluid and permeability, experiencing less parasitic load from pumps, and being technologically ready and widely used for heat exchange in shallow geothermal systems. Commercial application of closed-loop geothermal technology to deep high-enthalpy systems is now feasible given advances in drilling technology. However, the technology it uses has been questioned due to differences in heat transport capacities of convective flow within the wellbores and conductive flux in the surrounding rock. Here we demonstrate that closed-loop geothermal systems can provide reasonable temperature and heat duty for over 30 years using multiple laterals when installed in a suitable geological setting. Through use of two analytical methods, our results indicate that the closed-loop geothermal system is sensitive to reservoir thermal conductivity that controls the level of outlet temperature and interference between wells over time. The residence time of the fluid in the horizontal section, calculated as a ratio of the lateral length to flow rate, dictates heat transport efficiency. A long vertical production section could cause large drops in fluid temperature in a single lateral production system, but such heat loss can be reduced significantly in a closed-loop system with multiple laterals.

Understanding the flow and heat transfer in fractured geothermal reservoir is critical for the development of enhanced geothermal system (EGS) in the future. Under the framework of discrete fracture network, a thermal-hydraulic coupled model is proposed to evaluate the heat extraction performance of multilateral wells in fractured reservoirs. Five cases with varying numbers of branch wells considering well orientation are compared. In addition, we analyze the heat extraction performance response of multilateral wells in fractured reservoirs to the operating parameters. Results demonstrate the minimal effect of the increasing number of branch wells on the production temperature, while impacts on the well pressure are much greater. The injection pressure is observed to decrease significantly as the number of branch wells increases, resulting in a reduced reservoir flow resistance and increased net thermal energy by reducing pump energy consumption. For the same case, increasing the number of intersections between wells and fractures reduces the production temperature and injection pressure. Parameter sensitivity analysis reveals heat production to increases with the mass flow rate, well length and well spacing, and decreases with increasing fracture permeability. This study is expected to provide a view for the application of multilateral wells in fractured geothermal reservoirs.

In the 21st century, climate change is a severe threat to the survival of the planet and humanity; to counter this threat, the significant role of renewable energy cannot be denied for sustainable development worldwide. The motive of this study is to examine the threshold level and asymmetric relationship between renewable energy and economic development in different regimes of the different income levels of 122 countries from 1995-2018 by using the novel technique Panel Smooth Transition Regression Model (PSTR). The results of the PSTR model suggest that the relationship between Renewable Energy and the Economic Growth of these selected countries is nonlinear. Furthermore, in most countries, there is a significant and positive relationship between renewable energy and economic growth in the high regime, except the higher-income nations has a significant and positive relationship in both low and high regimes. Overall full sample shows a significant and positive relationship between renewable energy and economic growth. Recommendations based on this study for these countries include: 1) energy-efficient resources should be adopted to increase renewable energy consumption. 2) The conventional energy consumption share should be reduced to improve the environmental quality for a sustainable future.

The choice of condenser cooling option for concentrating solar power (CSP) plants is likely to affect their techno-economic feasibility. In view of this, an attempt has been made to assess relative techno-economics and net life cycle CO2-eq emissions mitigation (LCCM) potential for 50 MW nominal capacity wet-cooled and dry-cooled parabolic trough solar collector (PTSC) and dry-cooled solar power tower (SPT) based CSP plants with 6.0 h of thermal energy storage for two potential locations in India. It was observed that though dry cooling is likely to save significant amount of water (∼92%) in PTSC based plants, the same shall result in higher capital cost, higher performance penalty and higher parasitic power requirements leading to around 20% higher levelized cost of electricity (LCOE) as compared to wet-cooled PTSC based plants. It was also observed that the dry-cooled SPT based plants shall be able to deliver up to 4.5% higher annual electricity output and LCOE is also likely to be lowered by 13% than wet-cooled PTSC based plants. Considering emissions embodied and emissions associated with water transport/extraction from the source and water treatment, the estimation of LCCM from the PTSC and SPT based CSP plants have also been undertaken.

Ensuring power system reliability under high penetrations of variable renewable energy is a critical task for system operators. In this study, we use a loss of load probability model to estimate the capacity credit of solar photovoltaics and energy storage under increasing penetrations of both technologies, in isolation and in tandem, to offer new understanding on their potential synergistic effects. Increasing penetrations of solar PV alter the net load profile on the grid, shifting the peak net load to hours with little or no solar generation and leading to diminishing capacity credits for each additional increment of solar. However, the presence of solar PV decreases the duration of daily peak demands, thereby allowing energy-limited storage capacity to dispatch electricity during peak demand hours. Thus, solar PV and storage exhibit a symbiotic relationship when used in tandem. We find that solar PV and storage used together make a more significant contribution to system reliability: as much as 40% more of the combined capacity can be counted on during peak demand hours compared to scenarios where the two technologies are deployed separately. Our test case demonstrates the important distinction between winter and summer peaking systems, leading to significantly different seasonal capacity values for solar PV. These findings are timely as utilities replace their aging peaking plants and are taking energy storage into consideration as part of a low carbon pathway.

To enhance the performance of the thermodynamic systems, reduce the pollutants emission to the environment, and decline the fuel utilization, waste heat recovery methods are in high interest. In this paper, a new configuration of an integrated solid oxide fuel cell and gas turbine combined with a biogas reforming cycle is presented for the cogeneration of power and hydrogen. The thermal energy discharged from the SOFC-GT system is used to supply the energy required for the reforming reaction in the biogas reforming cycle for hydrogen production. Comprehensive thermodynamic and thermoeconomic modeling has been performed using EES software. Also, a parametric study has been performed to demonstrate the effect of different parameters on the main performance metrics of the devised system. The results revealed that the energy efficiency and exergy efficiency of the proposed combined system have increased compared to the SOFC-GT system by 23.31 % and 28.19 % , respectively. The net output power and hydrogen production rate are obtained by 2726 kW and 0.07453 kg / s , respectively. From the exergy viewpoint, the afterburner causes a considerable amount of exergy destruction for the system by approximately 26 % of the total exergy destruction rate. Besides, the sensitivity analysis revealed that by increasing the inlet temperature of the fuel cell, the cell voltage reaches a maximum value at a temperature of 679 K and then decreases. Moreover, the total exergy destruction rate and SUCP of the cogeneration system is calculated by 1532 kW and 9400 $ / GJ , respectively.

The Savonius rotor is one of the simple and cost-effective vertical axis drag type devices for hydropower generation. The main drawback of the Savonius hydrokinetic turbine is its low performance due to negative torque developed by returning blade profile. In this paper, the performance of modified V-shaped rotor blades with different V-angles ranging from 90° to 40°, by maintaining fixed edge length, arc radius and aspect ratio of 0.7 is investigated. The numerical analysis is carried out to estimate the optimum V-angle by maintaining 70 mm depth of water with an inlet velocity of 0.3090 m/s. The numerical study revealed that, for 80° V-angle rotor blade profile, the maximum coefficient of power was found to be 0.2279 at a tip speed ratio of 0.9. This optimum V-angle model was used for experimental analysis to study the effect of aspect ratio ranging from 0.7 to 1.75 using top, middle and bottom plates by maintaining 140 mm depth of water and inlet velocity of 0.513 m/s. The rotor blade with two endplates and one middle plate with an aspect ratio of 1.75 has shown a significant increase of performance by 86.13% at a tip speed ratio of 0.86 as compared to turbine blade with two endplates.

In the last few decades, the energy demand is increasing globally which, given the present dependency of the energy generation on fossil fuels, results in a continuous increase in CO2 emissions. In an isolated electric grid system like in the SIDS, the majority of the electricity is produced by fossil fuels, therefore most of the SIDS nations are now focusing on Variable Renewable Energy sources (VREs). VREs such as wind and solar are hardly predictable and bring instabilities in the electric power system if not buffered by a storage system. Here we investigate the possibility of using Seawater Pump Storage Hydropower Systems (S-PSHS) as a renewable energy storage solution in an isolated electric grid. For this, the island of Curacao (one of the SIDS nations) is used as proof of the concept. For detecting potential locations for the S-PSHS sites on the island, GIS application was developed. The application of this conceptual proposed solution in similar systems is straightforward and it can be easily upscaled in other geographies. The concept of using seawater for the pumped hydro project is not common in practice and it is anticipated to have technical, environmental and financial challenges which are discussed in this paper.

Electrocatalytic CO2 reduction (ECO2R) is an environment-friendly way to convert CO2 into profitable products. Amine solution recently has been employed as an electrolyte in ECO2R but suffers from low efficiency. Herein, aqueous solutions containing different amine-based deep eutectic solvents (DESs) were used as electrolytes for CO2 reduction. The effect of different DESs on the CO2 reduction was investigated at Ag, Cu, and Zn metal electrodes. Tafel and electrochemical impedance spectroscopy (EIS) were applied to understand the CO2 reduction. DES in aqueous solution facilitates the CO2 reduction to CO with higher faradaic efficiency of CO (FECO) than amine solutions and a mixture of hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD). Both HBD and HBA have an influence on CO2 reduction. [Monoethanolamine hydrochloride] [methyldiethanolamine] ([MEAHCl][MDEA]) gives high FECO, 71% FECO at −1.1 V vs RHE at Ag electrode, 33% higher than [MEAHCl][MEA]. Experimental results and EIS analysis reveal that the facilitation of CO2 reduction to CO probably stems from a synergistic effect of nano-size agglomerate dispersion on Ag-surface, bicarbonate formation, exchange current density, and Cl− ions present in DESs. These findings present a feasible method to employ the aqueous MDEA-based DES solution as an electrolyte for CO2 reduction.

Fresh green asparagus is prone to lignify after harvest due to its high respiration rate and secretion of secondary metabolites regulated by enzymes generated during storage. In this work, a dense hemicellulose-based coating containing hemicellulose, cellulose nanofibers, and montmorillonite (MMT) was prepared and used as a coating to reduce the respiration rate of green asparagus, with which the shelf life of green asparagus was prolonged from 5 days to 7 days. Alkyl ketene dimer (AKD) was used as a hydrophobizer and a crosslinking agent to reduce humidity sensitivity by introducing hydrophobic fatty acid chains to nanoparticles for increased structural stability and respiratory barrier property hemicellulose-based film in high humidity conditions. Our study proved that AKD modified coating with nature-derived nanomaterials could effectively increase respiratory barrier property, slow down the secretion of lignification-involved enzymes, and regulating the conversion of phenolic compounds to the lignin monomers.

9 figures, 5 tables.-- Supplementary information available, Active and durable electrocatalysts for the oxygen evolution reaction (OER), capable of replacing noble metal catalysts, are required to develop efficient and competitive devices within the frame of the water electrolysis technology for hydrogen production. In this work, we have investigated tantalum based catalysts supported on carbon nanofibers (CNF) for the first time. The effect of CNF characteristics and the catalyst annealing temperature on the electrochemical response for the OER have been analyzed in alkaline environment using a rotating ring disc electrode (RRDE). The best OER activity and oxygen efficiency were found with a highly graphitic CNF, despite its lower surface area, synthesized at 700 °C, and upon a catalyst annealing temperature of 800 °C. The ordering degree of carbon nanofibers favors the production of oxygen in combination with a low oxygen content in tantalum oxides. The most active catalyst exhibited also an excellent durability., The authors want to thank the Ministerio de Economía, Industria y Competitividad (MICINN) and FEDER for the received funding in the project of reference ENE2017-83976-C2-1-R, and to the Gobierno de Aragón (DGA) for the funding to Grupo de Investigación Conversión de Combustibles (T06_17R). J.C. Ruiz-Cornejo acknowledges DGA for his PhD grant. D. Sebastián acknowledges the MICINN for the Ramón y Cajal research contract (RyC-2016-20944).

As a green, low-carbon and renewable energy, the geothermal energy has attracted great attentions. Abundant geothermal resources are hosted in several depleted oilfields. Geothermal development in abandoned oilfields has its advantages that operators are familiar with the geographic environment, geological conditions, and drilling and development techniques in the oilfield. In this study, a thermo-hydro- mechanical multi-field coupling mathematical model was established with data from Liubei Buried Hill reservoir in North China Oilfield. Then, the geothermal development in abandoned high-temperature oilfields was simulated, and the sensitivity of the geothermal development effect to well patterns, fracturing conditions, and working media was analyzed. The results show that the well pattern of one-injector and four-producer leads to the largest heat-exchange area. The hydraulic fracture model causes earlier thermal breakthrough but produces more heat than the non-fractured model. CO2 has the better working fluid performance and leads to the better geothermal development effect than water. This study provides a theoretical basis for the high-efficiency development of geothermal energy in abandoned oilfields, and a guidance for research on geothermal development model and fracturing design.

In the present study, the performance of breakwater-integrated OWC (oscillating water column) wave energy converter devices is analyzed under the action of unidirectional regular and irregular incident waves. Two different types of OWC devices: (i) LIMPET device (sloping-face OWC device) and (ii) quarter-circle-shaped front wall OWC device are considered for the present study. Detailed derivations of the parameters associated with the performance of the OWC devices under the action of irregular waves are provided. To analyze the efficiency of the OWC devices in real sea conditions, the Bretschneider Spectrum is taken as the incident wave spectrum along with nine sea states represent the local wave climate at the OWC plant site Pico, Portugal. The annual-averaged plant efficiencies of the two aforementioned OWC devices are analyzed as a function of chamber length, submergence depth, turbine rotor diameter, and rotational speed of the Wells turbine. It is observed that the annual-averaged plant efficiency can be enhanced significantly with appropriate combinations of chamber length, submergence depth, and turbine characteristics.

Estimating the heat transfer in deep underground geothermal systems is a challenging task. The concept of explicitly describing the heat transfer between phases has been shown superior to the conventional approach but the heat transfer coefficient of fractures is still ambiguous. In this work, a definition of the lower and upper bound of the heat transfer coefficient between rock and flowing fluid in a single rock fracture is derived and validated with almost 250 experiments from other studies. The resulting values range between 8 and 260 W/m2 °C, with upper bounds roughly a factor 10 larger. Further, as shown in this work, the assumption of local thermal equilibrium can result in lower production temperatures than the assumption of heat transfer between phases depending on reservoir conditions. A dimensionless number is derived to distinct those cases and to determine the lower limit of the outflow temperature in any scenario. The results of this work enable a quantification of the value range of the heat transfer coefficient from laboratory experiments and allow a tabulation of the heat transfer coefficient for all kind of scenarios. The presented results can be used in discrete fracture models for an improved prognosis of production temperatures.

The quality of decisions in the renewable energy sector is as good as the quality of available data. This makes data quality a cornerstone in renewable energy system planning, designing, operation, and assessment. Unfortunately, such data is not always available and usually is cost-prohibitive. One solution for this issue is using the data of few representative days (RDs) instead of the full year for reduced costs of the data itself and the system simulations. A new framework is proposed in this study to distinguish these RDs based on meteorological features. The new framework represents an end-to-end pipeline, starting with measurements, data curing, feature extraction, clustering, and representative year construction. The analysis showed that increasing the number of RDs indeed improves the representativeness of the reconstructed year with disagreement indices as low as 1.041. Including system-irrelevant meteorological parameters was found to increase the disagreement index between original data and reconstructed year from 0.206 to 0.989. The proposed autoencoder feature extraction approach outperformed the conventional statistical one, especially for shallow autoencoders, where the disagreement index was reduced from 1.564 to 1.001. Finally, a brief case study of a standard solar water heating system was performed using TRNSYS v18 software to verify the proposed approach, where the absolute percentage deviation in the annual solar fraction was found to be only 0.278%. This study takes the first steps towards offering decision-makers, designers, and modelers a framework that provides high-quality and high-resolution data compatible with the elevating measurements and simulation cost.

Beet pulp is an extremely very wet organic waste derived from sugar production. It can be utilized for energy purposes, e.g. biogas production or as very valuable fodder for animals, mainly horses. The high moisture content (80%) in beet pulp makes it an adequate feedstock for the hydrothermal carbonization process. Therefore, this study is focussed on the hydrothermal carbonization of beet pulp. The following parameters were studied: temperatures of 180, 200, and 220 °C through 1, 2, 3, and 4 h of residence time. The optimal conditions of the process were determined (220 °C and 1 h), based on the physical and chemical properties of solid product hydrochar. The ultimate and proximate analyses, high heating value, energy and mass yields, and energy densification ratio were investigated. The obtained hydrochars were of a coal-like solid biofuel, with high heating values much higher than raw feedstock (c.a. 150% higher). The combustion performance and kinetics of hydrochar based on TGA were determined, indicating better combustion. Moreover, the fibre analysis of hydrochar, supported by infrared spectra and scanning microscope analysis confirmed the changes in its structure. Concluding, organic waste, beet pulp, is of great potential as an energy source using the hydrothermal pretreatment process.

Two-phase closed thermosyphon heat exchangers (TPCTs) have considerable potential for use in ground source heat pump systems. This paper proposes a new metal-polyethylene TPCT that uses water as the working fluid and is composed of a galvanized steel pipe and a polyethylene pipe. The heat transfer rate characteristics of the metal-polyethylene TPCT were studied using a constant-temperature water bath test bench. The experimental results show that the metal-polyethylene TPCT has the best heat transfer rate when the vacuum degree and filling ratio are 1.00 kPa and 12.5%, respectively. The average heat transfer rate increased as the temperature of the heat source and the flow rate of the cooling water increased. Finally, a sandbox test bench was built, which provided seepage and non-seepage experimental conditions for the metal-polyethylene TPCT. In the sandbox experiment, the heat transfer rate capacity of the metal-polyethylene TPCT was initially studied and compared with that of a single U-tube heat exchanger, and the heat transfer rates were similar. When the evaporation section length was 0.5 m, the heat transfer rates were 34.89 W/m and 111.75 W/m under non-seepage and seepage conditions, respectively. The experimental results show that the metal-polyethylene TPCT is feasible as a new type of ground heat exchanger.

Tidal stream turbines (TST) deployed in open-water energetic sites are often unintentionally at yaw to the incoming flow that causes performance degradation and deflection of the wake. Wake steering is a popular concept in wind arrays where the upstream turbine is operated intentionally at yaw to steer the wake away from a downstream turbine. To explore such arrangements for TST arrays, a synergistic experimental and numerical campaign was undertaken to characterize a TST performance and wake deflection subjected to ±15° yawed inflow. The near-wake characterization study was performed using complementary acoustic Doppler velocimetry measurements and 3D computational fluid dynamics. The experiments show a ∼10% reduction in the maximum power coefficient. In the near field, the deflected wake morphed into an elliptical shape due to the formation of two counter-rotating vortices. The wake deflection results in enhanced momentum transfer and dissipation, leading to accelerated energy recovery. When the upstream turbine is yawed, available kinetic energy in the flow for the downstream turbine is at least 50% higher with the turbine array in a staggered configuration compared to the inline configuration. Our results provide guidance in reducing the cross-stream and downstream spacing between turbine units in an array.

Catalytic processes play an important role in the valorization of biomass for the production of biofuels. In this context, the effect of desilication of MOR zeolite (H-MOR-D) on the esterification of oleic acid as a model reaction for biomass conversion was investigated. Zeolite catalysts were characterized by BET, TG, NH3-TPD, XRD, XRF, FTIR and 27Al MAS NMR analysis and the results showed that the alkaline treatment caused a decrease in crystallinity and removal of sites with greater acid strength of the zeolite precursor. The conversion of oleic acid into methyl oleate catalyzed by H-MOR was less (44%) than that obtained by the treated zeolite H-MOR-D (70%), suggesting that the catalytic activity in the MOR structure does not depend only on the high density of strong acid sites. DFT calculations showed that, bulky molecules suffer molecular distortions within the confined voids, consequently the adsorption enthalpy is highly unstable limiting the formation of intermediates and thus contributing to the lower reaction rate observed experimentally in H-MOR zeolite. Desilication should be considered in projects for the synthesis of new catalysts type zeolite for the conversion of biomass crude or pre-treated, in which bulky molecules prevail.

The viability of the store-on grid (SoG) scheme model across 13 selected Sub-Saharan African (SSA) countries was investigated. The individual country's datasets applicable to the SoG scheme and a typical industrial building as a baseline prosumer were used in the evaluation. Two SoG scheme scenarios (A and B) based on solar photovoltaic (PV) module prices were used in this analysis. The electricity tariffs under the SoG scheme were compared with the time of use rates for the selected SSA countries. The analysis results revealed that the scheme could be viable in only nine and four out of 13 countries under scenario A and scenario B, respectively, with high lending interest rate in some countries being the key hindrance. Under the SoG scheme model, solar PV systems in all the selected countries could feed about 15.65–39.25% of the generated energy to the grid. The government tax in the range of 1.95–3.38 and 2.48–4.31 c$/kWh could be collected from the energy fed to the grid under SoG scheme scenario A and scenario B, respectively. Overall, the SoG scheme exhibits greater potential as an energy business model to foster rooftop solar PV technology adoption in developing countries.

A barium-modified zeolite (Ba-ZEL) catalyst was developed via co-precipitation technique followed by thermal treatment (calcination) at different temperatures (600, 700 and 800 °C). The thermal stability, elemental composition, surface functional groups, crystallographic structure, textural characteristics, basic strength and surface morphology of the Ba-ZEL catalyst were determined using TGA/DTA, EDX, FTIR, XRD, BET, CO2-TPD and SEM techniques, respectively. The biodiesel production process conditions, such as catalyst loading, alcohol to oil ratio, temperature and time, were optimized using a central composite design approach. The Ba-ZEL composite calcined at 700 °C was selected as a representative catalyst due to its high activity for the waste frying oil (WFO) conversion, resulting in a maximum biodiesel yield of 93.17 ± 0.02% under optimum conditions (3.0 wt% catalyst loading, 12:1 methanol to WFO ratio, 65.38 °C reaction temperature and 2 h reaction time). The produced biodiesel, which was characterized by the FTIR and GC-FID analyses, contained sufficient ester groups and was in accordance with the specifications of EN 14214. Additionally, its physicochemical properties met ASTM D6751 specifications. Moreover, the Ba-ZEL700 catalyst was reused for five cycles upon regeneration using n-hexane washing followed by reactivation at 110 °C for 12 h.

This paper examines the gap between the design and in-situ performance of solar streetlight interventions in two humanitarian settings. Displaced settlements often lack street lighting and electricity. Given that off-grid solar streetlights produce surplus energy, we hypothesized that this energy could be made available for daily usage, to improve system performance and provide further energy access to displaced populations. We recognize, however, that solar streetlight performance and longevity have typically been poor in remote and refugee settings. Eleven solar streetlights were fitted with ground-level sockets and their performance monitored, in two displaced settlements: a refugee camp in Rwanda and an internally displaced population settlement in Nepal. Considerable performance gaps were found across all eleven systems. Inefficient lights and mismatching system components were major issues at both sites, reducing targeted designed performance ratios by 33% and 53% on average in Rwanda and Nepal, respectively. The challenges of deploying these types of systems in temporary settlements are outlined and a number of suggestions are made to guide future developments in the design and implementation of sustainable solar streetlight interventions.

The paper deals with the cavitation at tongue of a pump-turbine in pump mode, including the typical patterns, unsteady behaviors, and the influence on pump performance and fluid-borne noise. Visualization experiments were conducted under different flow rates and rotational speeds for variation cavity regimes. The results show the patterns can be divided into three regimes with cavitation development: bubble cavitation, cloud cavitation, and lock cavitation for the gas-lock phenomenon and performance plummet. The rotor-stator interaction and jet-wake flow could affect the cavitation generation. The blade passing effect is the leading cause of bubble clusters periodic collapsing or shedding at the early stages of cavitation, while playing a small role as cavities become thick and evaporation rate rises. The combined action of the attached vortex (re-entrant jet) and the depression by pressure gradient outside cavity surface account for the shedding at the developed cloud cavitation stage. Based on the noise measurement by hydrophone at the outlet, the broadband sound in the range of 1000 HZ-2000 Hz can be used for cavitation detection since it can be rarely influenced by operating conditions under non-cavitation.

Solar tower systems show significant prospects based on their room for improvement in the solar thermal industry. Despite not being an entirely new concept, multi-tower systems have not been extensively studied in the literature yet. An optical optimization model is presented to evaluate the feasibility of dual-tower systems, where each heliostat can select the most convenient receiver. There is a number of optimization variables, which makes it essential to implement a fast optical algorithm capable of evaluating the field optical efficiency. Taking advantage of the tower central receiver's axial symmetry, an integration method is proposed to work out the individual spillage for each heliostat. As a result, an optimal design has been accomplished where 32 representative days (with several time-points each) have been taken into account to assess the yearly-averaged optical efficiency of the whole solar field. Thus, it can be concluded that a ∽1.5% increase in the annual optical efficiency can be achieved with respect to the analogous single tower system.

The recent increase in Renewable Generation (RG) has prompted many states, utilities, and other stakeholders to improve the methods used to determine the value of RG in efforts of replacing the Net Metering approach. However, these studies result in a wide range of values. This paper proposes a methodology based on the RG valuation studies conducted in recent years. The method includes the most common cost and benefit components considered in these studies and adopts a comprehensive method to calculate each component. The main categories include avoided energy, avoided generation capacity, avoided transmission capacity, avoided system losses, price hedging benefits, environmental benefits, and grid integration costs. A realistic case study emulating a large utility is also conducted to illustrate the application of the proposed method. The results show that all the main components can be estimated based on detailed system models or simulations. The results also illustrate some of the data challenges associated with such a study.

Due to the large size of free fatty acid molecules, they cannot diffuse into Al–Si–P Zeotype pores in the biofuel production process. Therefore, in the current work, to rectify this problem, in the synthesis of Al–Si–P zeotype by hydrothermal method, various weight percentages of the carbon casting and ultrasound waves for the uniform of the materials were used. Moreover, to enhancement the acidic strength and catalyst performance, Ceric oxide was accommodated on the Al–Si–P zeotype structure by sono-solvothermal synthesis. TPD-NH3, FESEM, HRTEM, BET-BJH, and EDX analyses were utilized for characterizing the samples developed in the present work. BET analysis has revealed that the optimized percentage of charcoal active is 4 wt %. By adding the sonication technique at the stage accommodating Ceric oxide on Al–Si–P zeotype, the conversion percentage increased from 77 to 94%. Test of the capability of modified Al–Si–P Zeotype with sonication and carbon casting to produce biofuel from waste oil delivered a conversion of 91.5%. Kinetic studies have shown that reaction of oil to biofuel is of the first degree, and the modified Al–Si–P Zeotype with sonication and carbon casting has the highest rate constant (0.0014 min−1) among all of the synthesized samples.

Geothermal energy resources are necessary to meet the increasing energy requirements worldwide and reduce the impact of climate change, particularly in developing countries. The aim of this study is the investigation of the low-enthalpy geothermal system of Pismanta, in the Central Andes of Argentina, to evaluate the possibility of power generation or direct use applications. Results indicate a circulation of meteoric water to the reservoir located in the Iglesia Basin, reaching a maximum depth of 2500 m. A background heat flow of 60 mW/m2 raises the temperature of the reservoir to approximately 95 °C resulting in a mean thermal gradient of 30 °C/km. The preliminary evaluation of four binary cycle energy conversion plants suggests a gross power generation range of 30–280 kW and the capacity of using the remaining heat for direct use applications such as drying of fruits, greenhouses, food processing and membrane distillation processes to solve arsenic problems in freshwater, among others.

In this study, three SBCs are developed as (i) SBC with phase change material (PCM: waste cooking oil and C4H4O3), (ii) a novel SBC with nanocomposite PCM (NPCM), and (iii) a SBC without NPCM. The novel proposed cooker integrated with NPCM (MgAl2O4/Ni/Fe2O3-PCM) was experimentally developed and its performance was evaluated using fuzzy logic and Cramer's rules, and image processing techniques. The results indicated that the implementation of a bar plate absorber coated with MgAl2O4/Ni-doped, Fe2O3 nanoparticles, and integrated with PCM increases the cooker's internal temperature up to 164.12 °C. The used nanocomposite materials were in the average particle size of 20 μm. The cooking materials were verified with the temperature in the segmentation process. The NPCM indicated the SBC's thermal performance enhancement of 11% in comparison with the SBC with PCM and without NPCM. Additionally, the overall thermal performance of SBCs without NPCM, with PCM, and with NPCM was obtained as 24.90–33.90%, 24.77–45.20%, and 31.77–56.21%, respectively. Moreover, the temperature of the bar plate absorber was achieved as 163.74 °C, 147 °C, and 113.34 °C for the SBC with NPCM, PCM, and without NPCM, respectively, under the solar radiation of 1,037 W/m2.

Shadow-bands are a low cost alternative when a precision solar tracker is not available. Adequate precision may be achieved if the measured diffuse irradiance is corrected to account for the sky portion blocked by the shadow-band. The isotropic sky assumption leads to a systematic under estimation of diffuse irradiance. Several correction methods have been proposed to take into account the anisotropic effects. However, their performance at a given site depends on the dominant local climate. In this work, it is shown that the local adaptation of shadow band correction methods results in a significant improvement in the diffuse irradiance measurement's accuracy. Nine well-known correction methods are implemented and tested (both in their original and locally adapted versions) for the Pampa Humeda region of southeastern South America. In absence of local adaptation, only one of the pre-existing methods improves the simple isotropic model. All locally adapted versions perform similarly well and outperform significantly the original methods. A new model based on the parametrization of Battle's model is proposed. It provides the best performance compared to all locally adapted pre-existing models, under all-sky and discriminated sky conditions.

Recently, Biodiesels are found high popularity as environmentally friendly and renewable fuels. Suitable combustion, appropriate atomization process, high flash point, and proper cetane number approved biodiesels as potential alternative for petroleum-based diesel fuels. Since, characteristics of biodiesels as well as biodiesel-diesel blends are directly related to their viscosity, an accurate approach is required for prediction of this important transport property. Therefore, this study tries to compare the accuracy of different empirical and intelligent paradigms for estimation of biodiesel-diesel blends. For this regard, the best topology of adaptive neuro-fuzzy inference systems (ANFIS) and least squares support vector machines (LSSVM) are determined at first, and then their predictive performances are compared with five empirical correlations in literatures. Combination of statistical study and ranking analysis justified that the LSSVM with polynomial kernel is the most accurate approach for the considered matter. The designed model estimated kinematic viscosity of 636 biodiesel-diesel blends with an excellent AARD = 0.754%, MAE = 0.03, RAE = 1.98%, RRSE = 2.3%, MSE = 0.003, RMSE = 0.05, and R2-value of 0.9997.

Access to sustainable energy source is crucial for healthcare facilities to deliver their services. Hybrid solar energy systems (HSES) are seen as a strong solution given the proximity of the Philippines to the equator. This study addresses the knowledge gap in the estimated energy consumption profile of Philippine rural health units (RHU) using easily replicable questionnaire and work sampling technique. The estimated energy consumption profile was used to determine the optimal HSES design and benefits. The RHU of Los Banos, Laguna was considered, and simulation of different energy system configurations was performed in the HOMER Pro software. Two scenarios were considered: a grid-connected and an off-grid RHU. The estimated average scaled load of the facility is ∼92 kWh per day. Estimates were validated against actual consumption, with 15–21% error. Results of the simulations show that a solar photovoltaic panel-grid system is optimal for the grid-connected scenario and can reduce cost of electricity by ∼35%. Meanwhile, a solar photovoltaic panel-generator-battery system is optimal for the off-grid scenario and can reduce cost of electricity by ∼61%. In both scenarios, the solar component is estimated to contribute ∼71–85% of the total annual energy production and can help reduce greenhouse gas emissions.

In urban areas, vertical axis wind turbines have been installed on both sides of the road and rooftop. Compared with rooftop, vertical axis wind turbines mounted on the side of a building have a larger swept area with longer blades, and the effect of tip vortices can be reduced at the same time. Around the building, there are several high wind speed regions that can provide more wind energy. In this paper, a high-resolution numerical method composed of overset grid and adaptive mesh refinement techniques is adopted to verify the feasibility of vertical axis wind turbines mounted on the side of the building. Firstly, the complex flow field around the building is simplified into the flow field around the cylindrical building. Five typical flow regions with different flow conditions are determined: windward zone, crosswind zone, tailwind zone, recirculation zone and leeward zone. Secondly, wind turbines are installed evenly around the building. The simulation results show that the energy output of wind turbines in tailwind zone can be increased by 120% compared with the reference value. Thirdly, multiple wind turbines are coupled with the building. In order to get the optimal arrangement, power outputs of four arrangements are compared for the best choice. The results indicate that the arrangement with six wind turbines in crosswind zone and tailwind zone can achieve the best performance. Through changing the rotational directions, the forward blades of wind turbines can be close to the wall, and the energy output of all the wind turbines around the building can be improved.

An effective approach for synthesizing green and sustainable biodiesel fuel from low-value vegetable oils has been explored. Herein, a series of catalysts of zinc supported on zirconia (xZn/ZrO2) were successfully synthesized, characterized, and applied for the production of biodiesel from Litsea cubeba kernel oil (LCKO) through the transesterification process. The results showed that the monoclinic phase structure of the prepared catalysts transformed to the more stable tetragonal phase structure after supporting different Zn loadings (≥5%). Compared with the pure ZrO2, the highly dispersed Zn species on the surface of xZn/ZrO2 could be divided into Zn oxide and ZnOH+, which could promote the transesterification of LCKO. Thus, the 7%Zn/ZrO2 catalyst exhibited the best catalytic activity of the LCKO conversion 82.5%, which was attributed to the positive effects of both the ZrO2 support and Zn species. Furthermore, the various reaction parameters (such as reaction time, stirring rate, nCH3OH:nLCKO, catalyst amount, and reaction temperature) were investigated systematically and optimized carefully. And a possible mechanism of the transesterification process catalyzed by Zn/ZrO2 catalysts was also proposed. Finally, the physical properties of the as-synthesized biodiesel accorded with the current international biodiesel standards.

Recent investigations verified CaO2 accelerated hydrolysis of lignocellulose, but its residue caused a harmful oxidizing environment. This study therefore proposed the combined CaO2 pretreatment and zero-valent iron (ZVI) addition to enhance high-solid anaerobic digestion of wheat straw, trying to eliminate negative effect of residual oxides. Effects of CaO2 pretreatment without/with ZVI addition on digestion performance were investigated. Results showed that in non-ZVI added digesters, as CaO2 dosage increased, total production of SCOD and VFAs increased linearly, while activities of coenzyme F420 and electron transport system were negatively correlated. Pretreatment using appropriate CaO2 dosage indirectly increased biogas production by promoting hydrolysis and acidification. Comparably, initial ORP in ZVI-added digesters sharply declined below −350 mV, which was suitable for methanogen growth. ZVI significantly improved activities of cellulase, hemicellulase, acetic kinase and coenzyme F420, with the highest improvement percentages of 138%, 48%, 35% and 58%, respectively. Since ZVI could provide electrons for conversion of CO2 to CH4, compared with non-ZVI added digesters (R0-R4), methane content in ZVI-added digesters (RZ0-RZ4) increased by 8.1%, 9.0%, 11.2%, 17.0% and 18.0% successively. Consequently, 0.6 g/g VS CaO2 pretreatment combined with 0.4 g/g VS ZVI addition achieved the maximum methane production, increasing by 35.6% compared to control digester.

An hybrid floating platform concept, combining a wind turbine with wave energy converter devices, has been proposed. This paper conducts a further exploration of these synergies analyzing the utilization of the wave energy converters to assist the platform water ballast system on the compensation for variations on the sea state conditions. An experimental campaign has been performed for a preliminary evaluation of this approach. It is limited, for simplification, to five different sea state conditions in head wave situation. However, it allows the study of the main design principles that should be followed to develop the approach in a more complex scenario. The experimental results indicate that energy wave converters assist the water ballast system in the tested sea state conditions, and even extend the operational sea state range. Moreover, it indicates that wave energy converters located at downwind and upwind sides of the platform have different roles in the compensation of the platform dynamics. The first ones are dedicated to the production of platform restoring moments while the seconds are harvesting the power that should be supplied to the downwind of the wave converters. The case study considers the application of oil-hydraulic technology in wave energy converters.

An effective air staging strategy is of great importance for achieving low emissions and sensible heat losses through flue gas extraction. In cases where a commercially available system needs to be optimised, often the only viable measure is the modification of process parameters. In this work, the aim is to (1) Discover a combination of the most suitable process parameters based on a multi-criteria decision-making method and (2) To unveil relevant correlations between the two process parameters under study (PA/SA ratio and excess air), emissions and combustion temperatures. A modified commercial small-scale hot water wood pellet boiler was installed into a laboratory heating system. Nine different cases have been addressed within a parametric study, differing in the PA/SA ratio and overall excess air. Emissions, temperatures inside the combustion chamber and the flow rate of air entering the combustion chamber were measured. A low PA/SA ratio of 0.53 (54.7% reduction from factory settings), combined with a low O2 concentration in the flue gases of 5.26% (39.8% reduction from factory settings), and the elimination of infiltration air resulted in a simultaneous reduction of NOx and CO emissions by 14.4% and 93.9% respectively and a flue gas sensible heat loss reduction of 31.6%.

Hydrodynamic damping is a key factor that influencing the amplitude of structural vibration under resonance conditions. In this study, the one-way FSI energy balance method by loading structure mode onto flow field is applied to simulate the hydrodynamic damping. Based on the good solution of vortex shedding frequency, structure natural frequency and mode shape, it provides a good accuracy on both flow field and structural field by predicting the hydrodynamic damping well with deviations less than 10.4%. On the basis, the hydrodynamic damping characteristics of different vibration displacements and the lock-in region are studied and analyzed in detail. Results found that the hydrodynamic damping ratio increases with the increasing of vibration displacement. A displacement interval within 6 × 10−5 m–1.2 × 10−4 m can be detected when the hydrodynamic damping ratio is slightly affected by vibration displacement. It is proved that the value of hydrodynamic damping depends on the combined area of hydrodynamic force and structural velocities. The hydrodynamic damping in the lock-in region changes nonlinearly. Under the resonance condition, the disturbance of the fluid domain increases, and a negative damping value will appear, which will increase the structure vibration amplitude.

Systems involving more than one energy source, namely hybrid systems, can be arranged in different configurations and layouts depending on the available or used energy source, application and scale of the system. Despite an increasing awareness and penetration of renewable energy sources at different scales in many countries over the world, the adoption of hybrid and novel renewable systems is relatively scarce, especially at a small scale. This scenario is also presented from the point of view of the research of such systems. Therefore, the scope of the paper is to improve the knowledge regarding small-scale hybrid renewable energy systems performance and operation by investigating a novel trigeneration system based on a biomass fired steam cycle, wind turbine, photovoltaic panels and adsorption chiller. In the proposed system, the thermal energy recovered by the steam cycle is used to match the user thermal demand by means of a storage tank supplying directly heat to the user during winter, and driving the adsorption unit during summer. The electrical energy produced by the steam turbine, photovoltaic field and wind turbine is managed by a control system that integrates a bidirectional connection with the electric grid. The grid allows one to virtually store the electrical energy produced in excess and to recover it in part when needed by the user. In order to assess the system performance, a farm and residential buildings are considered as case study. The proposed system is modelled and dynamically simulated by means of Transient System Simulation software. In the paper, the dynamic operation of the system and the energy and economic performance of the system is assessed. The operation of the system is presented in a daily and monthly basis, while the global performance parameters of the system are reported considering a one-year period. The primary energy saving of the system is above 70% when a reference system based on natural gas, electric chiller and grid is considered. For this scenario, the Simple Pay Back of about 10 years is achieved. The results of the analysis show that the system is feasible from the technical and energy point of view, whereas its economic profitability is significantly affected by its cost and the reference system that is adopted by the user.

In this study, a new method of microwave-induced discharge over biomass-derived char (i.e., bio-char) spherical carriers was proposed. Bio-char spherical carriers were obtained through rational forming. The discharge intensity and temperature increase under discharge were measured to elaborate the quantitative relationship between microwave discharge and the temperature increase. The effect of bio-char properties on microwave-induced discharge was investigated. The results revealed that discharge achieved the highest electric–thermal conversion efficiency of 61.04%, and the heat generation ratio through the discharge in the initial 10 min was up to 69.08%. The graphitisation degree and transmission depth of microwaves can affect discharge intensity. A critical light intensity inducing hot spot effect exists under different working conditions, and exceeding the critical value led to the hot spot effect and a sudden increase in bed temperature, with a corresponding range of 2.48–5.76 V. The maximum temperature under microwave discharge reached 981 °C, with a heating rate of 376.4 °C/min. The method is potential in the field of value-added utilization of bio-char and microwave-promoted chemical processes.

With the increasing demand for environmental protection, CO2, as a natural refrigerant, has always been environmentally friendly and safe, which makes transcritical CO2 heat pump system attract more attention. The internal heat exchanger is employed to improve the performance of transcritical CO2 heat pump system to match the traditional heat pump circulation system. In this work, two evaluation methods are proposed, one is the actual operation thermal effectiveness of internal heat exchanger, the other is the actual increase rate of COP. Compared with the experimental results, the conclusions can be extracted that the actual increase rate of COP can effectively evaluate the impact of the internal heat exchanger on system performance. In addition, this research deeply analyzes the influence of the internal heat exchanger on exergy efficiency. The results show that the internal heat exchanger greatly reduces the exergy efficiency under the discharge pressure of 7310 kPa and the ambient temperature of 15 °C, and the difference value between the system with and without internal heat exchanger reaches 39%. However, the influence of the internal heat exchanger on exergy efficiency decreases with the increase of discharge pressure and ambient temperature, the minimum difference value is only 0.1% at 11000 kPa and 30 °C.

The peak period of an energy-generating wave is one of the most important parameters that describe the spectral shape of the oceanic wave, as this indicates the duration for which the waves prevail with respect to their maximum extractable energy. In this paper, a half-hourly peak wave energy period (TP) forecast model is constructed using a suite of statistically significant lagged inputs based on the partial auto-correlation function with an extreme learning machine model developed and its predictive utility is benchmarked against deep learning models, i.e., convolutional neural network (CNN/CovNet) and recurrent neural network (RNN) models and other traditional M5tree, Conditional Maximization based Multiple Linear Regression (MLR-ECM) and MLR models. The objective model (ELM) vs. the comparison models (CNN, RNN, M5tree, MLR-ECM, and MLR) were trained and validated independently on the test dataset obtained from coastal zones of eastern Australia that have a high potential for implementation of wave energy generation systems. The outcomes ascertain that the ELM model can generate significantly accurate predictions of the half-hourly peak wave energy period, providing a good level of accuracy relative to deep learning models in selected coastal study zones. The study establishes the practical usefulness of the ELM model as being a noteworthy methodology for the applications in renewable and sustainable energy resource management systems.

This study investigates the impact of monetary policy on renewable energy generation in Iran. It examines three types of renewable energy generation: total renewable energy generation; solid biomass and biogas energy generation; and the hydropower, solar, and wind group energy generation. The study uses the Kalman filter and vector autoregression (VAR) models to examine annual data from 1984 to 2016. The Kalman filter model showed that the money supply parameter moved with a steady trend, except for a sharp point during the Iran-Iraq War. A sharp point can be found for real interest rate parameter as well, although the time of global crisis and sanctions also affects this coefficient. The VAR model results indicate that only a shock to money supply can affect all the three renewable energy generation types.

A novel model reference adaptive system for the rotor position/speed estimation and sensorless operation of a brushless doubly fed reluctance generator with maximum power point tracking is presented. Its main advantage over the existing designs are the inherent robustness and stability afforded by the complete parameter independence of the reference model using only the measured currents of the converter-fed (secondary) winding. In addition, the respective stationary frame current components are estimated by the adaptive model using the voltage and current measurements of the grid-connected (primary) winding at line frequency, offering higher accuracy. The simulation and experimental results have demonstrated the excellent real and reactive power controller performance for typical operating characteristics of wind turbines.

Energy consumption and economic growth play an important role in the global policy debate among policymakers around the world. This is the first study to investigate the relationship between economic growth and energy consumption at the state level for the U.S. from 2000 to 2016. As opposed to country-level studies, a focus on states within a country allows for comparisons across more homogeneous entities. The four known hypotheses are tested: growth, conservative, feedback, and neutral, differentiating between renewable and non-renewable energy consumption. In order to address endogeneity, two strategies are developed: (1) a static analysis for 2016 where key policy covariates are gradually added to the model, and (2) a dynamic analysis using different generalized method of moments (GMM) estimators. The model is augmented using socioeconomic, regulatory and climatic variables, which allows for the evaluation of policies while facilitating a transition to renewable energy use. Overall, the results show that total energy consumption and non-renewable energy consumption support the feedback hypothesis. Results for renewable energy, industrial energy, and residential energy consumption show more support for the growth hypothesis. These results have policy implications in terms of optimizing decisions and investments to efficiently improve economic growth while reducing energy consumption.

Microalga biomass is a reliable bioenergy feedstock to produce green fuel owing to its high lipid and organic content. On the other hand, the microalgal biomass productivity as well as lipid accumulation widely depends on various cultivation factors - including nitrogen/phosphorus ratio and light-dark cycles (LD). This study investigated the effects of LD and NaNO3 (nitrogen) dose on the specific growth rate (SGR), biomass productivity (P), and intracellular lipid productivity (LP) of Chlorella kessleri. Response surface methodology (RSM) and support vector regression (SVR) based nonlinear empirical models were developed to forecast SGR, P, and LP. The laboratory data acquired based on central composite design (CCD) matrix, was utilized to establish the adequacy of the models. Bayesian optimization algorithm (BOA) was coupled with SVR to tune the hyperparameters automatically. The performance of the hybrid intelligence model (BOA-SVR) was better than RSM model for anticipating all the responses. Lastly, the crow search algorithm was combined with BOA-SVR to achieve the global optimal solution for maximizing SGR, P and LP, simultaneously. The maximum SGR, P, and LP were found to be 0.302 d−1, 45.31 mgL−1d−1, and 16.3 mgL−1d−1, respectively at the operating environments of LD of 12/12 (h/h) and NaNO3 dose of 10.92 gL-1.

Thermoelectric generators (TEGs) can convert heat into electricity directly. However, the thermal boundary conditions are intermittent and high temperature in most TEG systems. Therefore, thermal management of TEG systems is of great significance. It is an efficient technology to use phase change material (PCM) for thermal management of the TEG systems. PCM is applied to hot side of TEG in this study, and the phase change material-thermoelectric generation (PCM-TEG) system is set up. For the purpose of exploring the effect of the PCM on the output performance of TEG, the common TEG system is established to compare with PCM-TEG system. Furthermore, the effect of the heat transfer characteristics of PCM on TEG output performance is investigated and discussed in detail under different pulse transient thermal boundary conditions. Experimental results show that PCM can reduce the temperature fluctuation to protect TEG and extend the temperature difference operation time. The PCM of solid state, solid-liquid coexistence state and liquid state have different effects on reducing the temperature fluctuation. Besides, the PCM-TEG system cannot provide the peak output power provided by the common TEG system, but it is still beneficial to provide a stable output power.

Integration of solar photovoltaic systems to low-voltage distribution networks is witnessing an unprecedented growth in many parts of the world. Although solar photovoltaic generation is of significant benefit from a number of angles, exceedance of hosting capacity levels by such installations in low-voltage distribution networks continue to cause significant technical challenges in network operation, especially to the management of network voltage. Modern smart inverters are equipped with Volt-VAr and Volt-Watt control capabilities, which can assist in the management of network voltage levels. This paper provides a detailed analysis of the influence of different connection standards which cover these strategies on solar photovoltaic hosting capacity and their applicability in low-voltage distribution networks. Smart inverters with differing Volt-VAr and Volt-Watt control functions are modelled in the DIgSILENT PowerFactory platform. Influence of different connection standards on solar photovoltaic hosting capacity is analysed to investigate the most beneficial connection approach/es to address the issue of voltage violations. Furthermore, the work presented in this paper provides a greater understanding on the hosting capacity improvement by employing advanced inverter control functions where such improvements are subjected to locational aspects of inverters in low-voltage distribution systems.

Global electricity consumption has raised in the last century due to many reasons such as the increase in human population and technological development. To keep up with this increasing trend, the use of fossil resources has increased. But these resources are not environmentally friendly, and for this reason, many countries and governments are encouraging the use of green sources. Among these sources, PV technology is widely promoted and used due to its improved efficiency and lower prices for photovoltaic panels. Therefore, the importance of forecasting power production for these plants is necessary. In this work, two hybrid models were proposed (CNN-LSTM and ConvLSTM) to effectively predict the power production of a self-consumption PV plant. To confirm the efficiency of the proposed models, the LSTM model was used as a baseline for comparison. The three models were trained on two datasets, a univariate dataset containing only the power output of the previous days, while the multivariate dataset contains more features (weather features) that affect the production of the PV plant. The time frames for the forecast ranged from one day to one week ahead of time. The results show that the proposed methods are more accurate than a normal LSTM model.

Presented paper identifies the possible corrosion problems related to animal waste incineration since it is a key issue for their use in the power sector. Cow dung as an example of animal-origin biomass is examined in terms of high-temperature corrosion and slagging hazards in comparison with commonly used mixed straw. Results of the laboratory-scale corrosion studies of pure ash deposits on two steel alloys: 16Mo3 and 10CrMo9–10 are reported. Selected steel types are commonly used in boiler construction for superheaters and waterwalls – parts of a boiler that are most exposed to the high-temperature corrosion risk. The corrosion experiments were carried out under oxidizing conditions at 460 °C, 510 °C and 560 °C for 168 h. To determine the corrosion rate the mass of steel samples was measured after 24, 72 and 168 h. For a better understanding of the corrosion process, a detailed chemical analysis of ashes was conducted together with SEM-EDS analysis of the corrosion products. Ash melting and deposition behavior of both ashes were predicted according to 11 indices. It was found that cow dung and mixed straw ash differ significantly in terms of quantitative chemical compositions and ash melting characteristics. Cow dung ash is characterized by a high concentration of alkali compounds (2.57 wt% Cl, 30.6 wt% CaO, 5.56 wt% K2O) together with high phosphorus content typical for animal manure. The presence of alkali chlorides in the cow dung ash deposits led to a build-up of chlorides on the steel surface, which caused accelerated corrosion. At 560 °C the corrosion rate was over 3 times higher for cow dung ash than for mixed straw ash. The corrosion occurred due to the formation of low-melting FeCl2 mixtures since chlorine- and iron-rich particles were found in the crevices and cracks within deposits. The results clearly demonstrated the high corrosive potential of animal-origin biomass and therefore indicate the potential problems related to its thermal conversion process. These adverse effects can be reduced by ash removal and maintaining the temperature of the heating surfaces below 560 °C.